STIRLING, Scotland — Add exposure to polluted air to the list of possible health issues associated with flying on airplanes. A recent study found that flight crews are sickened by their regular exposure to air supplies contaminated by engine oil or other common aircraft fluids.

Scientists at the University of Stirling, led by Dr. Susan Michaelis, surveyed a cohort of 200 flight crew members and recorded a clear pattern of chronic and acute health problems, from dizziness and headaches to vision and breathing problems.

Is flying on airplanes worse for our health than thought? A recent study found that flight crews and pilots are often sickened by polluted cabin air caused by engine oils and other aircraft fluids.

Dr. Michaelis calls her team’s findings “significant” and suggests air travel come with a health warning.

“There is a clear cause-and-effect relationship linking health effects to a design feature that allows the aircraft air supply to become contaminated by engine oils and other fluids in normal flight,” she explains in a university release. “This is a clear occupational and public health issue with direct flight-safety consequences.”

The researchers conducted two separate surveys of the flight crew cohort. One survey examined the pilots’ health. It found that 88% were aware of exposure to potentially dangerous chemicals in the aircraft’s air supply. About 65% reported some kind of specific health effects, and 13% had died or experienced chronically poor health.

The other test examined specific oil leak incidents. Eighty percent of oil leaks examined involved only fumes, and each of the leaks occurred when the airplanes were in flight or preparing for flight. Crews reported fumes both before and after the leaks in two-thirds of the reported leaks, and nearly all of the incidents (93%) caused symptoms in the crew ranging from in-flight impairment to incapacitation. About 75% of these incidents caused symptoms in multiple flight crew members.

The researchers say more than 3.5 billion passengers and 500,000 aircrew were exposed to low levels of engine oils in 2015.

“We know from a large body of toxicological scientific evidence that such an exposure pattern can cause harm and, in my opinion, explains why aircrew are more susceptible than average to associated illness,” says co-author Vyvyan Howard, a professor of pathology and toxicology at the University of Ulster. “However, exposure to this complex mixture should be avoided also for passengers, susceptible individuals and the unborn.”

The research is hoped to eventually improve health risks for flight crews and those who regularly fly on airplanes.

The full study was published in World Health Organization’s Public Health Panorama.